Mobile internet access with proxy support

ABSTRACT

The present invention is directed to a method, a node arrangement and a mobile node for registering a Care-of-Address on behalf of a Mobile Node at a Home Agent in a home network of said Mobile Node when the Mobile Node is connected to a foreign network. The method comprises the steps of: providing at least one advertisement message to said Mobile Node ( 710 ) from a network node arrangement ( 722 ) in the foreign network ( 724 ), which advertisement message identifies the node arrangement ( 722 ) as a Home Agent for said Mobile Node ( 710 ), and receiving a request for an IP-address from said Mobile Node ( 710 ) at said node arrangement ( 722 ) as a response to said advertisement message, and providing 0 an IP-address to said Mobile Node ( 710 ) from said node arrangement ( 722 ) as a response to the request, which IP-address is valid for the Mobile Node ( 710 ) at the foreign network ( 724 ), and registering a Care-of-Address from said node arrangement ( 722 ) on behalf of said Mobile Node ( 710 ) at the Home Agent ( 712 ) in the home network ( 714 ) of said Mobile Node  710.

TECHNICAL FIELD

The invention described herein relates to communication between nodes incommunication networks. Embodiments of the invention relate tomanagement of network addresses for mobile nodes in communicationnetworks. Particular embodiments of the invention relate to nodes inwireless networks.

BACKGROUND OF THE INVENTION

Mobility in connection with communication networks is often aprecondition. The ability to move within a network and/or betweenvarious networks is particularly desirable in connection with mobilewireless terminals, e.g. such as cell phones or such as laptops etcprovided with WLAN functionality or similar. A similar mobility is oftendesired for other terminals, e.g. such as wired Personal Computers (PCs)or similar.

As is well known to those skilled in the art, a solution for providingmobility in connection with the Internet and similar networks has beenprovided by the Internet Engineering Task Force (IETF). To this end theIETF has standardized a communication protocol called Mobile IP, orsimply MIP. Mobile IP allows mobile devices to move from one network toanother while maintaining a permanent IP-address. The basic features ofMobile IP are e.g. described in the IETF specification RFC 3344. Updatesare e.g. added in IETF specification RFC 4721 and further developmentsare e.g. described in the specification RFC 3775.

Mobile IP provides an efficient and scalable mechanism for roamingwithin the Internet and similar networks. Through the use of Mobile IP anode may change its point-of-attachment to the network without changingits IP-address. This allows the node to maintain transport andhigher-layer connections while moving between networks. Mobile IP ismost often found in wired and wireless environments where users need tocarry their mobile devices (Mobile Nodes) across multiple networks thatare in fact reached on different IP-addresses. Mobile IP may for examplebe used in roaming between overlapping wireless systems, for examplebetween WiFi, WiMax and/or 3G telecommunication networks and similar.

FIG. 1 is a schematic illustration of an exemplifying and well knownMobile IP system 100, e.g. based on the IETF specification RFC 3344. Ascan be seen in FIG. 1 the system 100 comprises a Mobile Node 110, a HomeAgent 112, a Foreign Agent 122 and a Correspondent Node 120. Variousdesigns of the Mobile Node 110 (MN), the Home Agent 112 (HA), theForeign Agent 122 (FA) and the Correspondent Node 120 (CN) are wellknown per se to those skilled in the art and there is no need for adetailed description. Nevertheless, a short background will be providedbelow.

As can be seen in FIG. 1 the MN 110 is arranged to operativelycommunicate with the HA 112 or the FA 122 via the home network 114 orthe foreign network 124 respectively. In turn, the HA 112 and the FA 122are arranged to communicate with each other via a communication network130 (e.g. the Internet or similar). In addition, the HA 112 is arrangedto operatively communicate with the CN 120 via said communicationnetwork 130. In particularly, the HA 112 and the FA 122 are arranged tooperatively enable communication between the MN 110 and the CN 120 overthe network 130, irrespective whether the MN is connected to the homenetwork 112 or the foreign network 124.

The exemplifying MN 110 in FIG. 1 is a terminal, a host or a router orsimilar that changes its point of attachment from one network orsub-network to another without changing its IP-address with respect tonodes that may communicate with the MN 110. In this way the MN 110 cancontinue to communicate with other Internet nodes and similar at anylocation using its (constant) IP-address. Here, it is assumed that alink-layer connectivity to a point of attachment is available and thatthe MN 110 comprises suitable hardware and software, e.g. in the form ofan interface that is suitable for utilizing the available link-layerconnectivity, and a client that enables the MN 110 to access the networkin question and nodes or similar that is available therein as is wellknown to those skilled in the art.

The exemplifying HA 112 in FIG. 1 is a router or similar connected tothe home network 114 of the MN 110. The HA 112 serves as the anchorpoint for communication with the MN 110. In particular, the MN 112tunnels data packets or similar for delivery to the MN 110 when the MN110 is away from its home network 114. In the exemplifying system 100shown in FIG. 1 the HA 112 tunnels packets received from the CN 120 andaddressed to the MN 110 at its Home Address (HoA), by forwarding thepackets to a Care-of-Address (CoA) via a tunnel 132 established betweenthe HA 112 and the FA 122, which is the reachable point for the MN 110in the foreign network 124. Such tunneling is well known to thoseskilled in the art.

The exemplifying FA 122 in FIG. 1 is preferably a router or similar thatfunctions as the point of attachment for the MN 110 when the MN 110roams to the foreign network 124. In other words, the FA 122 ispreferably a router in the foreign network 124 visited by the MN 110,which router provides mobility services to the MN 110 while registered.The FA 122 de-tunnels and delivers the data packets to the MN 110 thatwere tunneled by the HA 112 of the MN 110. For data packets sent by theMN 110, the FA 122 may serve as a default router for registered MobileNodes (MNs).

The CN 120 is a peer or similar with which the MN 110 is communicating.The CN 120 may be mobile or stationary.

The following steps provide an exemplifying outline of the operation ofthe Mobile IP protocol in the exemplifying Mobile IP system 100 shown inFIG. 1.

-   -   a) The mobility agents (i.e. the FA 122 and the HA 112 enabling        mobility for the MN 110) advertise their presence to the MN 110.        As is well known, this can e.g. be done by means of Agent        Advertisement messages or similar, which e.g. may comprise at        least one Care-of-Address (CoA) and a flag indicating whether        the mobility agent is a Home Agent or a Foreign Agent.    -   b) The MN 110 receives at least one of these advertisements and        determines whether it is located on its home network 114 or on        the foreign network 124.    -   c) If the MN 110 detects that it is located on the home network        114 it may operate without mobility services. If returning to        its home network 114 from being registered elsewhere, the MN 110        deregisters with its HA 112 through the exchange of Registration        Request and Registration Reply messages or similar.    -   d) If the MN 110 detects that it has moved to the foreign        network 124 it registers with the FA 122 by sending a        Registration Request message or similar, which includes the        permanent IP-address (the HoA) for the MN 110 and the IP-address        for the HA 112 of the MN 110. In turn, the FA 122 performs the        registration process on behalf of the MN 110 by sending a        Registration Request or similar containing the permanent        IP-address for the MN 110 and the IP-address (the CoA) for the        FA 122 to the HA 112. As indicated above, the CoA can be        provided by the FA 122 in its advertisement messages (i.e. a        foreign agent CoA) or by some external assignment mechanism such        as DHCP or similar. The transportation of the MN 110 to the        foreign network 124 is illustrated in FIG. 1 by a MN 110 with        dashed lines at the home network 114 and a dashed arrow to the        MN 110 with solid lines at the foreign network 124.    -   e) When the HA 112 receives the Registration Request message or        similar from the FA 122 it updates its home list or similar by        associating the CoA of the MN 110 with the HoA of the MN 110.    -   f) The HA 112 then sends an acknowledgement to the FA 122.    -   g) The FA 122 in turn updates its visitor list or similar by        associating the HoA and/or the address for the HA 112 of the MN        110 with a media address for the MN 110 valid on the foreign        network 124 and relays the reply to the MN 110.

The following steps provide an exemplifying outline of the service phaseof the Mobile IP protocol in the exemplifying Mobile IP system 100 shownin FIG. 1.

-   -   1. When the CN 120 wants to communicate with the MN 110, it        sends an IP packet addressed to the permanent IP-address (the        HoA) of the MN 110.    -   2. The HA 112 then intercepts the packet and consults its home        list or similar to find out whether the MN 110 is currently        visiting any other network, e.g. finds out whether there is a        CoA registered for the MN 110.    -   3. Assuming that the HA 112 encounters a CoA registered for the        MN 110 it will construct a new IP header that contains the CoA        of the MN 110 as the destination IP-address. The original IP        packet comprising the HoA of the MN 110 is put into the payload        of this IP packet. The HA 112 will then send a down-link packet        to the CoA. This process of encapsulating one IP packet into the        payload of another IP packet is known as IP-within-IP        encapsulation, or tunneling. This has been illustrated in FIG. 1        by a tunnel 132 extending from the HA 112 to the FA 122.    -   4. When the encapsulated packet reaches the foreign network 124,        the FA 122 decapsulates the packet and finds out the HoA of the        MN 110. The FA 122 then consults its visitor list or similar to        see if it has an entry for the MN 110.    -   5. If there is an entry for the MN 110 in the visitor list, the        FA 122 retrieves the corresponding media address and relays the        packet to the MN 110 via the foreign network 124.    -   6. When the MN 110 wants to send an up-link packet to the CN        120, it forwards the packet to the FA 122, which in turn relays        the packet to the CN 120 using normal IP routing.

In contrast to the exemplifying network in FIG. 1, other networks maynot have an explicitly designated FA or similar. Instead an AccessRouter (AR) or similar may be used for providing access for a mobilenode to the network in question.

FIG. 2 is a schematic illustration of another exemplifying and wellknown Mobile IP system 200. The system 200 in FIG. 2 is substantiallythe same as the system 100 in FIG. 1. Hence, the same or similarreference numbers indicate the same or similar features. However, as canbe seen in FIG. 2 the FA 122 in FIG. 1 has been replaced by an accessrouter AR 222. Here, the foreign agent (FA) or similar can be perceivedas located in the MN 210, a so called co-located FA. Moreover, thetunnel 132 in FIG. 1 has been replaced by the tunnel 232 extending allthe way to the MN 210 in FIG. 2. The fact that the MN 210 serves as theendpoint of the tunnel 232 is illustrated in that the tunnel 232continues from the AR 222 to the MN 110, instead of ending at the FA 122as in FIG. 1. The well known Mobile IP system 200 in FIG. 2 will beelaborate in some detail below.

As schematically illustrated in FIG. 2, when the MN 210 enters theforeign network 124 comprising the access router 222 it obtains aco-located CoA. Typically, a co-located CoA is a local IP-addressacquired by the MN 110 through some external means. The co-located CoAmay e.g. be provided by the AR 222 or some other node or nodearrangement in the foreign network 124, or it may be dynamicallyacquired as a temporary IP-address by the MN 110 through DHCP orsimilar. Once in possession of a collocated CoA the MN 210 (or theco-located FA) registers the co-located CoA with its HA 112 so as tocreate a tunnel 232 in the same or similar manner as described abovewith reference to the tunnel 132 in FIG. 1. In case a co-located CoA isused the MN 210 (or the co-located FA) serves as the endpoint of thetunnel 232 and it is therefore the MN 210 (or the co-located FA) thatperforms decapsulation of the packets or similar tunneled to it. In thereverse direction, data packets or similar sent by the MN 210 to the CN120 may be delivered to the CN 120 using standard IP routing mechanismsin the same or similar manner as described above with reference to FIG.1.

The structure and function of the Mobile IP systems 100, 200 are wellknown to those skilled in the art and they are e.g. described in theIETF specification RFC 3344 and its ancillary specifications and insimilar documents from the IETF and others. Hence, there is no need fora more detailed description of the general and well known structure andfunction of the Mobile IP systems 100, 200. However, specific detailsassociated with embodiments of the present invention related to MobileIP and similar will be discussed later herein.

As described above, it is assumed that the MNs 110, 210 in the systems100, 200 respectively have the well known Mobile IP capability to signalits location to the Home Agent 112 so as to maintain a permanentIP-address while the MNs 110, 210 move from one network to another. Inother words, the MNs 110, 210 maintains a permanent IP-address withrespect to the CN 120 or similar nodes that may communicate with the MN110, 210. However, there are many IP devices that are not provided withMobile IP capability.

To this end a proxy based Mobile IP solution has been proposed withinthe framework of the IETF. The proxy based Mobile IP solution utilizes adedicated entity to provide mobility services for an unaltered andsubstantially mobility unaware IP device that has no or insufficientMobile IP capability. In particular, the solution is based on anexternal node or similar acting as a proxy node that registers thelocation of the device at a Home Agent and maintains reachability whilethe device is on the network in question.

FIG. 3 is a schematic illustration of an exemplifying proxy based MobileIP system 300 in which the proposed solution may be implemented. Thesystem 300 in FIG. 3 is similar to the system 100 in FIG. 1 in that itincludes the same or similar HA 112, home network 114, CN 120, foreignnetwork 124 and communication network 130. However, in contrast to theMN 110 in FIG. 1, it is assumed that the MN 310 in FIG. 3 is a node thathas the ability to physically access different networks 114, 124, buthas no or insufficient Mobile IP capability. Instead it is assumed thata Mobility Proxy Agent (MPA) offers a proxy mobility service for the MN310, e.g. by performing registration functions on behalf of the MobileNode 310. The MPA may e.g. be arranged in an access point, a basestation, an access gateway or a similar Access Router 322 (AR).

The following steps provide a basic outline of the operation of theproposed Proxy Mobile IP solution applied to the exemplifying system 300shown in FIG. 3. The steps are schematically illustrated in FIG. 4.

-   1a) The Mobile Node 310 performs an establishment and access    authentication and/or authorization with the Access Router (AR) 322    comprising the MPA.-   1b) The AR/MPA 322 exchanges Authentication, Authorization and    Accounting (AAA) messages with an AAA infrastructure (not shown in    FIG. 3) in the communication network 130 or in the home network 134    or possibly even in the home network 114 to perform authentication    and authorization of the Mobile Node 310. As is well known an AAA    infrastructure is commonly a part of modern communication networks    such as e.g. cellular 3G networks defined by standards provided from    the 3rd Generation Partnership Project (3GPP) (see e.g.    www.3GPP.org).-   2) The MN 310 sends an Internet Protocol Control Protocol (IPCP)    configuration request to the AR/MPA 322 in case of a Point-to-Point    protocol (PPP) to request for an IPv4 address. In particular, if the    Dynamic Host Configuration Protocol (DHCP) is used, the DHCP client    in the MN 310 sends a DHCPDISCOVER message to the AR/MPA 322.-   3) Triggered by step 2 the MPA in the AR/MPA 322 sends a Mobile IPv4    registration request (RRQ) to the HA 112 on behalf of the MN 310.    Here, it is suggested that the RRQ contains a care-of address (CoA)    for the AR/MPA 322.-   4) The HA 112 registers the session for the MN 310, assigns a Home    Address (HoA) and returns the HoA to the AR/MPA 322 in a    Registration Reply (RRP).-   5) The AR/MPA 322 responds back to the MN 310 to suggest the IPv4    address, which is the HoA provided by the HA 112. This happens in    response to step 2. If DHCP was used at step 2, the AR/MPA 322 sends    back a DHCPOFFER to the HA 112 with the IPv4 address for the MN 310    set to the received HoA.-   6) At this step, regular IPCP/NCP procedures get completed and the    IP stack of the MN 310 is ready to receive or send IP packets. If    DHCP is used, the regular DHCPREQUEST and DHCPACK messages are    exchanged and the IP stack of the MN 310 is configured with the    assigned IPv4 address, i.e. the HoA mentioned above.

Hence, as can be seen in FIG. 3, a proxy tunnel 332 is establishedbetween the HA 112 and the AR/MPA 322 with the effect that data packetsor similar sent from the CN 120 to the MN 310 will be tunneled(forwarded) by the HA 112 to the AR/MPA 322, which in turn forwards thedata packets to the MN 310 at the HoA that has been previously assignedas described above.

However, the proposed solution described above displays severaldrawbacks, particularly when devices such as the MN 310 without properMobile IP capability operate in the same network and/or networks asdevices such as the MN 110 or MN 210 with Mobile IP capability.

For example, FIG. 5 illustrates the exemplifying proxy Mobile IP system300 in FIG. 3 wherein a MN 210 provided with Mobile IP capability entersthe proxy based foreign network 324. Following steps 4-5 in the proposedsolution, when the MN 210 enters the proxy based foreign network 324 theHA 112 will provide the AR/MPA 322 with the HoA of the MN 210, whereuponthe AR/MPA 322 forwards the HoA to the MN 210. This is schematicallyillustrated in FIG. 5 by the arrow labeled “HoA” pointing at theschematic point of attachment for the MN 210 to the foreign network 324.Now, since the MN 210 is provide with Mobile IP capability it willrecognize that it is not at its home network 114 and it will thereforetreat the provided HoA as its new care-of address (CoA) and register theHoA with its HA 112 through the exchange of a Registration Request andRegistration Reply message as previously described with reference toFIGS. 1 and 2. As a result data packets or similar sent from the CN 120to the MN 210 will be forwarded by the HA 112 to the HoA in the homenetwork 114, i.e. not to the MN 210 in the foreign network 324. This hasbeen schematically illustrated in FIG. 5 by a thick arrow from the CN120 to the HA 112 and a thick arrow from the HA 112 to the HoA in thehome network 114. Hence, the data packets from the CN 120 will not reachthe MN 210, since it is in fact currently connected to the foreignnetwork 324.

In another example illustrated In FIG. 6 it is assumed that a MN 210provided with Mobile IP capability is connected to its home network 114.The MN 210 at its home network 114 has been indicated by a solidrectangle. Now, when the MN 210 enters the proxy based foreign network324—still being connected to its home network 114—the HA 112 willprovide the AR/MPA 322 with the Home Address (HoA) of the Mobile Node210, whereby the AR/MPA 322 provides the HoA to the MN 210 via theforeign network 324. This establishes a proxy tunnel 332 between the HA112 and the AR/MPA 322 as previously described with reference to FIG. 3,and data packets or similar sent from the CN 120 to the MN 310 will nowbe tunneled to the MN 210 via the tunnel 332 and the AR/MPA 322. Hence,any communication from the CN 120 to the MN 210 at the home network 120will be interrupted even though MN 210 is still connected to its homenetwork 114. The interrupted communication is illustrated in FIG. 6 by athick dashed line extending between the HA 112 and the MN 210 via thehome network 114. An uncontrolled interruption of this kind is typicallyimproper or even unacceptable. For example, the period for establishingthe proxy tunnel 332 and a communication between the HA 112 and the MN210 via the foreign network 324 will most likely be too long to beacceptable for many real time applications, e.g. such as ordinaryconversations and video conversations etc. Moreover, there is typicallyno guarantee that the quality of service required for the interruptedcommunication in the home network 144 can be provided in the new foreignnetwork 324, at least not within an acceptable period of time.

Hence, there is a need for an improved proxy based Mobile IP solutionthat mitigates or avoids one or several of the proposed proxy basedMobile IP solution discussed above.

SUMMARY OF THE INVENTION

The present invention provides an improved proxy based Mobile IPsolution, which has been accomplished according to a first embodiment ofthe invention directed to a network node arrangement arranged to beoperatively connected to a foreign network for communicating with atleast one Mobile Node, characterized in that said node arrangement isarranged to operatively provide at least one advertisement message tosaid Mobile Node, which advertisement message identifies said nodearrangement as a Home Agent for said Mobile Node, and arranged tooperatively receive a request for an IP-address from said Mobile Node asa response to said advertisement message, and arranged to operativelyprovide an IP-address to said mobile node as a response to the request,which IP-address is valid for the Mobile Node at the foreign network,and arranged to operatively register a Care-of-Address on behalf of saidMobile Node at another Home Agent in a home network of said Mobile Node.

A second embodiment of the invention is directed to a node arrangementcomprising the features of the first embodiment and is characterized inthat the node arrangement is arranged to operatively provide saidadvertisement message to said Mobile Node via a wired interface or a anair interface of the foreign network.

A third embodiment of the invention is directed to a node arrangementcomprising the features of the first embodiment and is characterized inthat the node arrangement is arranged to operatively receivecommunication from the Home Agent, and arranged to operatively forwardsaid communication to the Mobile Node via the foreign network.

A fourth embodiment of the invention is directed to a node arrangementcomprising the features of the first embodiment and is characterized inthat said node arrangement comprises an Access Router (AR) arranged tooperatively provide said advertisement, and receive said request for anIP-address, and provide said IP-address, and a Mobility Proxy Agent(MPA) arranged to operatively register said Care-of-Address on behalf ofsaid Mobile Node.

A fifth embodiment of the invention is directed to a node arrangementcomprising the features of the first embodiment and is characterized inthat said node arrangement is arranged to be operatively connected to acommunication network, and arranged to operatively register saidCare-of-Address via said communication network.

In addition, the present invention provides an improved proxy basedMobile IP solution, which has been accomplished according to a firstembodiment of the invention directed to a method for registering aCare-of-Address on behalf of a Mobile Node at a Home Agent in a homenetwork of said Mobile Node when the Mobile Node is connected to aforeign network,

The method comprises the steps of:

-   -   providing at least one advertisement message to said Mobile Node        from a network node arrangement in the foreign network, which        advertisement message identifies the node arrangement as a Home        Agent for said Mobile Node,    -   receiving a request for an IP-address from said Mobile Node at        said node arrangement as a response to said advertisement        message,    -   providing an IP-address to said Mobile Node from said node        arrangement as a response to the request, which IP-address is        valid for the Mobile Node at the foreign network, and    -   registering a Care-of-Address from said node arrangement on        behalf of said Mobile Node at the Home Agent in the home network        of said Mobile Node.

A seventh embodiment of the invention is directed to a method comprisingthe features of the sixth embodiment and is characterized in that saidmethod comprises the steps of providing said advertisement message tosaid Mobile Node via a wired interface or a an air interface of theforeign network.

An eight embodiment of the invention is directed to a method comprisingthe features of the sixth embodiment and is characterized in that saidmethod comprises the steps of:

-   -   receiving communication from the Home Agent at said node        arrangement in the foreign network, and    -   forwarding said communication from said node arrangement to the        Mobile Node.

A ninth embodiment of the invention is directed to a method comprisingthe features of the sixth embodiment and is characterized in that saidmethod comprises the steps of:

-   -   using an Access Router (AR) for providing said advertisement,        and receiving said request for an IP-address, and providing said        IP-address, and    -   using a Mobility Proxy Agent (MPA) for registering said        Care-of-Address on behalf of said Mobile Node.

A tenth embodiment of the invention is directed to a method comprisingthe features of the sixth embodiment and is characterized in that saidmethod comprises the steps of:

-   -   connecting the node arrangement to a communication network,    -   registering said Care-of-Address via said communication network.

Moreover, the present invention provides an improved proxy based MobileIP solution, which has been accomplished according to an eleventhembodiment of the invention directed to a Mobile Node arranged to beoperatively connected to a network node arrangement in a foreignnetwork, characterized in that said Mobile Node is arranged tooperatively receive at least one advertisement message from said nodearrangement, which advertisement message identifies said nodearrangement as a Home Agent for said Mobile Node, and arranged tooperatively transmit a request for an IP-address to said nodearrangement as a response to said advertisement message, and arranged tooperatively receive an IP-address from said node arrangement as aresponse to the request, which IP-address is valid for the Mobile Nodeat the foreign network, and arranged to operatively have aCare-of-Address registered by said node arrangement on behalf of saidMobile Node at another Home Agent in a home network of said Mobile Node.

A twelfth embodiment of the invention is directed to a Mobile Nodecomprising the features of the eleventh embodiment and is characterizedin that said Mobile Node is arranged to operatively receive saidadvertisement message from said node arrangement via a wired interfaceor an air interface of the foreign network.

A thirteenth embodiment of the invention is directed to a Mobile Nodecomprising the features of the eleventh embodiment and is characterizedin that said Mobile Node is arranged to operatively receivecommunication from the Home Agent via said node arrangement which isarranged to operatively forward said communication to the Mobile Nodevia the foreign network.

A fourteenth embodiment of the invention is directed to a Mobile Nodecomprising the features of the eleventh embodiment and is characterizedin that said Mobile Node comprises at least a first interfacearrangement for operatively communicating with said Home Agent via saidhome network, and at least a second interface arrangement foroperatively communicating with said Home Agent via said foreign network.

A fifteenth embodiment of the invention is directed to a Mobile Nodecomprising the features of the fourteenth embodiment and ischaracterized in that said Mobile Node is arranged to operativelyreceive communication simultaneously from said Home Agent via said homenetwork of said Mobile Node and via said node arrangement in saidforeign network.

A sixteenth embodiment of the invention is directed to a Mobile Nodecomprising the features of the eleventh embodiment and is characterizedin that said Mobile Node is arranged to operatively receivecommunication from said Home Agent via said home network on a first HomeAddress and via said node arrangement in said foreign network via aForeign Address.

Further advantages of the present invention and embodiments thereof willappear from the following detailed description of embodiment theinvention.

It should be emphasized that the term “comprises/comprising” or similarwhen used in this specification is taken to specify the presence ofstated features, integers, steps or components or similar, but does notpreclude the presence or addition of one or more other features,integers, steps, components or groups thereof or similar.

It should also be emphasised that the steps or similar of the methodsdefined in the appended claims may, without departing from the presentinvention, be performed in another order than the order in which theyappear in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration an exemplifying and well known MobileIP system 100,

FIG. 2 is a schematic illustration of another exemplifying and wellknown Mobile IP system 200,

FIG. 3 is a schematic illustration of a suggested known proxy Mobile IPsystem 300,

FIG. 4 is a schematic state diagram illustrating a basic outline of theoperational steps of the suggested proxy Mobile IP solution system 300in FIG. 3,

FIG. 5 is a schematic illustration of the proxy Mobile IP system 300 inFIG. 3 wherein a MN 210 with Mobile IP capability enters the proxy basedforeign network 324,

FIG. 6 is another schematic illustration of the proxy Mobile IP system300 in FIG. 3 wherein a MN 210 with Mobile IP capability is stillconnected to its home network 114 when it enters the proxy based foreignnetwork 324,

FIG. 7 is a schematic illustration of an exemplifying proxy Mobile IPsystem 700 according to an embodiment of the present invention,

FIG. 8 is a schematic illustration of the relevant parts of theexemplifying Mobile IP Node 710 of the system 700 shown in FIG. 7,

FIG. 9 is a flowchart illustrating the operational steps of anembodiment of the present invention,

FIG. 10 is a schematic illustration of the proxy Mobile IP system 700 inFIG. 7 with the addition of further communication paths,

FIG. 11 is a schematic illustration of another exemplifying proxy MobileIP system 800 based on the proxy Mobile IP system 700 in FIG. 7 but withanother home network 814.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Structure of a MobileIP-System According to a First Embodiment of the Invention

FIG. 7 is a schematic illustration of an exemplifying proxy Mobile IPsystem 700 according to an embodiment of the present invention. Theproxy Mobile IP system 700 comprises a Mobile Node 710 (MN) with aco-located FA, a Home Agent 712 (HA), a home network 714, aCorrespondent Node 720 (CN), an Access Router 722 (AR), a foreignnetwork 724 and a communication network 130. Further, as can be seen inFIG. 7 the AR 722 comprises a Mobility Proxy Agent (MPA).

The exemplifying proxy Mobile IP system 700 is similar to the proxyMobile IP systems 100, 200, 300 previously described with reference toFIGS. 1, 2 and particularly with reference to FIGS. 3 and 4. Hence, themobility provided for the MN 710 in the exemplifying Mobile IP system700 is preferably based on the IETF specification RFC 3344 or itssuccessor or similar, e.g. such as the updates in the IETF specificationRFC 4721 and/or such as the further developments IETF specification RFC3775.

It follows that the MN 710, the HA 712, the home network 714, the CN720, the AR/MPA 722, the foreign network 724 and the communicationnetwork 130 of the system 700 and various designs thereof are well knownper se to those skilled in the art and there is no need for a detaileddescription of the ordinary features and functions of these nodes andnetworks etc. However, particular aspects related to embodiments of thepresent invention will be further discussed below.

It is preferred that the MN 710 in the system 700 is a Mobile IP Node,e.g. as previously described for the MN 210 with reference to FIG. 2.Hence the MN 710 may be a terminal, a host or a router or similar thatchanges its point of attachment from one network or sub-network toanother without changing its IP-address with respect to nodes that maycommunicate with the MN 110. The MN 710 is preferably based on the IETFspecification RFC 3344 and/or its updates or successor or similar, e.g.such as the updates in the IETF specification RFC 4721 and/or such asthe further developments in the IETF specification RFC 3775.

Hence, it is assumed that the MN 710 has the Mobile IP capability tosignal its location to the Home Agent 712 so as to maintain a permanentIP-address with respect to the CN 120 and other nodes that maycommunicate with the MN 710. To maintain a permanent IP-address it ispreferred that the MN 710 is arranged to operatively register aCare-of-Address (CoA) or similar at the HA 712 or at an entity acting asthe Home Agent (HA) for the MN 710. The CoA or similar may e.g. beregistered in the same or similar manner as previously described withreference to FIG. 1 and/or FIG. 2.

Already here it should be clarified that the MN 710 accessing the AR/MPA722 in the system 700 will not register a care-of address (CoA) orsimilar IP-address directly at the Home Agent 712 (HA), e.g. aspreviously described with reference to FIGS. 1 and/or 2. On thecontrary, it is preferred that the CoA or similar is registered by theAR/MPA 722 on behalf of the MN 712. Hence, even if the MN 710 or similarwould be without the Mobile IP capability to register a CoA or similarat the HA 712 as described with reference to FIGS. 1 and 2 it couldnevertheless access the foreign network 724, whereupon the AR/MPA 722would provide the mobility service by registering a CoA or similar atthe HA 712 on behalf of the MN 710. Conversely, given that the MN 710 orsimilar is provided with the Mobile IP capability to register a CoA orsimilar with the HA 712 and given that the AR/MPA 722 acts as a HomeAgent as will be further elaborated later, the MN 710 will recognisethat it operates vis-à-vis a Home Agent in the foreign network 724 andit will therefore not attempt to register a CoA or similar at the HA712, even though it has this capability. Instead, the MN 710 willoperate without mobility services vis-à-vis the AR/MPA 722, which inturn registers a CoA or similar at the HA 712 on behalf of the MN 722.

As the observant reader realises, the function of the AR/MPA 722indicated above makes it possible to avoid situations leading to faultyaddressing as previously discussed with reference to FIG. 5, since theHA 712 will in fact be provided with a CoA or similar for the MN 710indicating that the MN 710 is in fact located at the foreign network724. In addition, it is possible to avoid situations with interruptedcommunication as previously discussed with reference to FIG. 6, sincethe HA 712 may continue the communication with the MN 712 at its HoA inthe home network 712 until communication has been safely establishedwith the MN 710 at its CoA or similar in the foreign network 724. Thiswill be elaborated in more detail later.

Before we proceed it should be added that the MN 710 preferablycomprises a Home Address (HoA) that is valid at the home network 714 asthe MN 710 moves between the home network 714 and the foreign network724 or similar, or moves between other networks, e.g. such as betweenthe foreign network 724 and another foreign network or similar. However,the HoA may be another identifier that enables the HA 712 to identifythe MN 710. It should also be added that it is preferred that the MN 710is arranged to operatively acquire an IP-address or similar from thevisited foreign network 724 and/or the AR/MPA 722 or similar node ornode arrangement in the foreign network 724.

Interior details of the MN 710 are shown in FIG. 8 providing a schematicillustration of the relevant parts of the MN 710. It is preferred thatthe MN 710 in FIG. 8 is provided with a first interface arrangement inthe form of a first antenna 810 and a first radio circuit 812 beingconnected to each other for enabling radio communication with the homenetwork 714 and the HA 712. It is preferred that the first radio circuit812 is a WiFi radio or similar local radio and that the home network 714is a local WiFi network or similar, e.g. based on the IEEE 802.11standard or similar. Hence, in the exemplifying system 700 in FIG. 7 itis preferred that the MN 710 is arranged to operatively communicate withthe home network 714 via a WiFi-based access, i.e. via a WiFi-basedinterface that is well known per se to a person skilled in the art.Further, as can be seen in FIG. 8, it is preferred that the radiocircuit 812 is connected to a control unit 850 arranged within the MN710 for controlling and supervising the general operation of the WiFiparts or similar of the MN 710. The control unit 850 may be implementedby means of hardware and/or software and it may comprise one or severalhardware units and/or software modules, e.g. one or several processorunits provided with or having access to the appropriate software andhardware required by the functions of the MN 710. The features andfunctions of a WiFi control unit as the control unit 850 or similar arewell known to those skilled in the art and are e.g. described in theIEEE 802.11 and no further description is needed.

Moreover, it is preferred that the MN 710 in FIG. 8 is provided with asecond interface arrangement in the form of a second antenna 810′ and asecond radio circuit 812′ connected to each other for enabling radiocommunication with the foreign network 724 and the AR/MPA 722 connectedthereto. It is preferred that that the second radio circuit 812′ is aWiMAX radio or similar regional radio and that the foreign network 724is a regional WiMAX network or similar, e.g. based on the IEEE 802.20standard or similar. Hence, in the exemplifying system 700 in FIG. 7 itis preferred that the MN 710 is arranged to operatively communicate withthe foreign network 724 via a WiMAX-based access, i.e. via a WiMAX basedinterface that is well known per se to a person skilled in the art.Further, as can be seen in FIG. 8, it is preferred that the radiocircuit 812′ is connected to the control unit 850 in the MN 710 forcontrolling and supervising the general operation of the WiMAX parts orsimilar of the MN 710. As already indicated above, the control unit 850may be implemented by means of hardware and/or software and it maycomprise one or several hardware units and/or software modules, e.g. oneor several processor units provided with or having access to theappropriate software and hardware required by the functions of the MN710. The features and functions of a WiMAX control unit as the controlunit 850 or similar are well known to those skilled in the art of WiMAXtechnology and are e.g. described in the IEEE 802.20 and no furtherdescription is needed.

The attention is now directed to the exemplifying HA 712 in FIG. 7. TheHA 712 is similar to the HA 112 as previously described with referenceto FIG. 1. Hence, it is preferred that the HA 712 is a router or similarconnected to the home network 714 of the MN 710. The exemplifying HA 712serves as the Mobile IP anchor point for communication with the MN 710according to the IETF specification RFC 3344 and/or its updates orsuccessor or similar, e.g. such as the updates in the IETF specificationRFC 4721 and/or such as the further developments in the IETFspecification RFC 3775. In particularly, the HA 712 is arranged tooperatively register a CoA or similar for the MN 710 so as to establisha tunnel for delivering data packets or similar to the MN 710 when theMN 710 is located at the foreign network 724. In the exemplifying system700 shown in FIG. 7 the HA 712 tunnels packets received from the CN 120to the MN 710 via a tunnel 732 established between the HA 712 and theAR/MPA 722, which is the reachable point for the MN 710 in the foreignnetwork 724 as will be further elaborated below.

Before we proceed it should be added that the CN 120 may be any suitablenode that is arranged to communicate with the HA 712 via thecommunication network 130. For example, the CN 120 may be a terminal, ahost or a router or similar and it may even be a peer or similar withwhich the MN 710 is communicating. The CN 120 may be mobile orstationary.

The attention is now directed to the Access Router 722 (AR) of thesystem 700. It is preferred that the foreign network 724 comprises an AR722 in the similar manner as previously described with reference to FIG.3 and the AR 322. Hence, it is preferred that the AR 722 is a node ornode arrangement or similar entity in the foreign network 724 thatprovides access to the foreign network 724 for mobile nodes such as theMN 710 and similar. The AR 722 may e.g. be an access point, a basestation, an access gateway or a similar node or node arrangementproviding access to the network 724.

In addition, it is preferred that the AR 724 comprises a Mobility ProxyAgent (MPA) or similar. It should be emphasised that in some embodimentsof the invention the MPA or specific parts or functions thereof may notbe directly comprised by the AR 724 but rather connected to oraccessible by the AR 722. In either case, for the sake of simplicity theAR and the MPA will be jointly denoted AR/MPA 722 in the following.

In general, as is well known to those skilled in the art, a proxy server(e.g. such as the proxy-part in the AR/MPA 722) is typically a server orsimilar, e.g. a computer system and/or an application program thatservices the requests of its clients (e.g. such as the MN 710) byforwarding requests to other servers (e.g. such as the HA 712). Theclient connects to the proxy server and requests a service, such as afile, a connection, a web page or some other resource available fromanother second server or similar. The proxy server provides the resourceby connecting to the second server and requesting the service on behalfof the client. A proxy server may alter the client's request or theresponse from the second server.

In view of the above it is preferred that the AR/MPA 722 offers a proxymobility service for the MN 710. In particular, it is preferred that theaccess-part of the AR/MPA 722 is arranged to operatively provide accessto the foreign network 724, whereas the proxy-part of the AR/MPA 722 isarranged to operatively provide mobility services on behalf of the MN710. Hence, it is preferred that the proxy-part of the AR/MPA 722 isarranged to operatively register a CoA or a similar IP-address at the HA712 on behalf of the MN 710 so as to establish a tunnel 732 between theHA 712 and the AR/MPA 722. It is also preferred that the proxy-partand/or the access-part of the AR/MPA 722 is arranged to operativelyprovide a foreign IP-address (HoA′) to the MN 710, which address can beused as the valid IP-address by the AR/MPA 722 with respect to theforeign network 724 and the MN 710. It is further preferred that theaccess-part of the AR/MPA 722 is arranged to operatively act as a HomeAgent for the MN 710 in the foreign network 724.

Function of a Mobile IP System According to an Embodiment of theInvention

Exemplifying functions of the Mobile IP will now be described withreference to FIG. 9 showing a flowchart illustrating the operationalsteps of an embodiment of the present invention, and FIG. 10 showing aschematic illustration of the exemplifying proxy Mobile IP system 700 inFIG. 7 with the addition of further communication paths.

In a first step S1 it is preferred that the exemplifying proxy Mobile IPsystem 700 is activated so as to be operative. It is also preferred thatthe MN 710 is within range of at least the home network 714.

In a second step S2 it is preferred that the mobility agents—i.e. theAR/MPA 722 and the HA 712 enabling mobility for the MN 710 in the system700—advertise their presence to the MN 710 via the air interfacesprovided by the WiFi-based home network 714 and the WiMAX-based foreignnetwork 724 respectively.

As is common in connection with Mobile IP it is preferred the HA 712announces itself as the Home Agent (HA) for the MN 710 at the homenetwork 714. In addition, it is preferred that the access-part of theAR/MPA 722 announces itself as the Home Agent (HA) for the MN 710 at theforeign network 724.

Announcing a node as a Home Agent for a Mobile Node is well known tothose skilled in the art of Mobile IP and similar technologies and it isalso described in the above mentioned specification RFC 3344, updated ine.g. the specification RFC 4721 and further developed as described inthe specification RFC 3775. For example, as is well known, theannouncements of the Home Agent may e.g. be performed via AgentAdvertisement messages or similar messages transmitted from the HA 712and AR/MPA 722 respectively. It is preferred that the announcements fromthe HA 712, AR/MPA 722 are set up by the operator of the networks 714,724 respectively. In fact, the networks 714, 724 may have the sameoperator or there may be an agreement and/or cooperation between theoperators of the networks 714, 724, which facilitates the setup ofvarious nodes such as the HA 712 and the AR/MPA 722 and the distributionand/or allocation of IP-addresses as will be further discussed below.

In a third step S3 it is preferred that the MN 710 is located within thecoverage area of the WiFi-based home network 714. Hence, the MN 710 willreceive the Agent advertising messages or similar from the WiFi-basedhome network 714 and the HA 712.

Since the HA 712 announces itself as a Home Agent, the MN 710 willdetect that it is accessing the home network 714. Hence, the MN 710 willregister its presence at the home network 714, e.g. through the exchangeof Registration Request and Registration Reply messages or similar withthe HA 712. In particular, it is preferred that the MN 710 is registeredat the HA 712 with a Home Address (HoA) that is the valid IP-address forthe MN 710 at the home network 714. The HoA can e.g. be provided by theHA 712 and/or a similar node or node arrangement with in the homenetwork 714. Hence, a communication path between the MN 710 and the HA712 has been established via the home network 714 as indicated by thefat arrow extending from the HA 712 to the MN 710 in FIG. 10. Thus, datapackets or similar addressed by the CN 720 to the MN 710 at its HoA canbe forwarded by the HA 712 to the MN 710 at its HoA in the home network714.

In the reverse direction, data packets or similar sent by the MN 710 tothe CN 120 may e.g. be delivered to the CN 120 using standard IP routingmechanisms. For example, the data packets or similar may be deliveredvia the HA 712, which in turn forwards the data packets to the CN 120.Alternatively, the data packets or similar may e.g. be delivereddirectly to the CN 120. The reverse direction from the MN 710 to the CN120 has not been explicitly indicated in FIG. 10.

The observant reader realizes that the MN 710 operates without mobilityservices vis-á-vis the home network 714 and the HA 714, i.e. without anyCoA or similar. The HA 712 knows the location of the MN 710 due to itsdirect registration at the HA 712 and there is no need for the MN 710 tosignal its location to the HA 712 by registering a CoA or similar aspreviously described with reference to e.g. FIG. 1 or 2.

In a fourth step S4 it is preferred that the MN 710 is also locatedwithin the coverage area of the WiMAX-based foreign network 724. Hence,the MN 710 will also receive the Agent advertising messages or similarfrom the WiMAX-based foreign network 724 and the AR/MPA 722.

Since it is preferred that the accessing-part of the AR/MPA 722announces itself as a Home Agent the MN 710 will detect that it isaccessing a home network. The MN 710 will therefore register itspresence at the access-part of the AR/MPA 722 as being the Home Agentfor the MN 710 at the foreign network 724. The registration at theAR/MPA 722 acting as a Home Agent for the MN 710 may e.g. be performedthrough the exchange of Registration Request and Registration Replymessages or similar as is well known per se by those skilled in the art.

In particular, it is preferred that the MN 710 is registered at theaccess-part of the AR/MPA 722 with a second Home Address (HoA′) that isthe valid IP-address for the MN 710 at the foreign network 724. The HoA′may also be denoted foreign HoA or foreign IP-address. The HoA′ may e.g.be provided by the AR/MPA 722 and/or a similar node or node arrangementwithin the foreign network 724, or by some external assignment mechanismsuch as DHCP or similar. Hence, a communication path between the MN 710and the AR/MPA 722 has been established via the foreign network 724.

The observant reader realizes that the MN 710 operates without mobilityservices vis-á-vis the foreign network 724 and the AR/MPA 722, i.e.without any CoA or similar. The AR/MPA 722 announces itself as the HomeAgent for the MN 710 at the foreign network 724 and the MN 710 willtherefore register itself directly at the AR/MPA 722, which implies thatthe AR/MPA 722 knows the location of the MN 710. Hence, since theaccess-part of the AR/MPA 722 acts as a Home Agent there is no need forthe MN 710 to signal its location by registering a CoA or similar aspreviously described with reference to e.g. FIG. 1 or 2. Instead it ispreferred that the mobility services for the MN 710 is provided by theproxy-part of the AR/MPA 722 while the MN 710 is registered at theforeign network 722 as will be described below.

In a fifth step S5 it is preferred that once the MN 710 has beenregistered at the AR/MPA 722 with a HoA′ as described above theproxy-part of the AR/MPA 722 sends a registration request (RRQ) orsimilar to the HA 712 on behalf of the MN 710.

In a sixth step S6 it is preferred that the method is ended. However,this should not be understood so as to limiting the exemplifying methodto a single performance of the steps therein.

For enabling the identification of the MN 710 in the RRQ or similar itis preferred that the RRQ contains the HoA of the MN 710 valid at thehome network 714 and the HA 712, which HoA is preferably comprised bythe MN 710 as previously described. However, the HoA of the MN 710 maybe replaced by another identifier that enables the HA 712 to identifythe MN 710 and/or associate the MN 710 with the received RRQ or similar.It is also preferred that the RRQ or similar contains a care-of address(CoA) for the AR/MPA 722, i.e. not a CoA for the MN 710 at the foreignnetwork 724 as is otherwise common, c.f. the systems 100, 200 describedabove with reference to FIGS. 1 and 2. It is preferred that the RRQ orsimilar is acknowledged by the HA 712 sending an acknowledge messageback to the proxy-part of the AR/MPA 722.

Knowing the CoA for the AR/MPA 722 and hence indirectly the HoA′ for theMN 710 at the foreign network 724 enables the HA 712 to forward datapackets or similar sent to the MN 710 at its ordinary HoA in the homenetwork 714 to the CoA for the AR/MPA 722. In turn, knowing the HoA′ forthe MN 710 in the foreign network 724 enables the AR/MPA 722 to forwardsaid data packets or similar to the MN 710 at the HoA′ in the foreignnetwork 724.

Hence, as can be seen in FIG. 10, a proxy tunnel 732 is establishedbetween the HA 712 and the AR/MPA 722 with the effect that data packetsor similar sent from the CN 120 to the MN 710 can be tunneled by the HA712 to the AR/MPA 722, which in turn forwards said data packets to theMN 710 at the HoA′ in the foreign network 724.

In the reverse direction, data packets or similar sent by the MN 710 tothe CN 120 may e.g. be delivered to the CN 120 using standard IP routingmechanisms. For example, the data packets or similar may be deliveredvia the AR/MPA 722, which in turn forwards the data packets to the CN120. Alternatively, the data packets or similar may e.g. be delivereddirectly to the CN 120. The reverse direction from the MN 710 to the CN120 has not been explicitly indicated in FIG. 9.

It should be clear from the steps S1-S5 above that the MN 710 accessingthe AR/MPA 722 does not register a care-of address (CoA) or similarIP-address directly at the HA 712. On the contrary, the registering of aCoA or similar will be handled by the proxy-part of the AR/MPA 722 onbehalf of the MN 712. Hence, even if the MN 710 or similar would bewithout the Mobile IP capability to register a CoA or similar at the HA712 as described with reference to FIG. 3 it can nevertheless access theforeign network 724, whereupon the AR/MPA 722 will provide the mobilityservices by registering a CoA or similar at the HA 712 on behalf of theMN 710. Conversely, given that the MN 710 or similar is provided withthe Mobile IP capability to register a CoA or similar with the HA 712and given that the AR/MPA 722 acts as a Home Agent, the MN 710 willrecognise that it operates vis-à-vis a Home Agent in the foreign network724 and it will therefore not attempt to register a CoA or similar atthe HA 712, even though it has this capability. Instead, the MN 710 willoperate without mobility services vis-à-vis the AR/MPA 722, which inturn registers a CoA or similar at the HA 712 on behalf of the MN 722.

As previously indicated in connection with the description of the MN710, the function of the AR/MPA 722 makes it possible to avoidsituations leading to faulty addressing as previously discussed withreference to FIG. 5. In addition, it is also possible to avoidsituations leading to interrupted communication as previously discussedwith reference to FIG. 6, since the HA 712 may continue thecommunication with the MN 712 at its HoA in the home network 712 untilcommunication has been safely established with the MN 710 at its CoA orsimilar in the foreign network 724. This is can be achieved due to thefact that the HA 712 has access to both the HoA registered in the HA 712for the MN 710 at the home network 714 and the CoA registered in the HA712 for the MN 710 at the foreign network 724. Hence, the HA 712 can bearranged to operatively select to continue the communication with the MN710 at its HoA in the home network 712 until the communication has beensafely established with the MN 710 at its CoA in the foreign network724.

In fact, even if communication of data packets and similar with the MN710 via the foreign network 724 has been safely established the HA 712may nevertheless be arranged to continue routing the communication tothe MN 710 at its HoA in the home network 714, at least for a period oftime. The routing path may e.g. be selected depending on the quality ofservice (QoS) available in a specific routing path. Similarly, the HA712 may be arranged to operatively route communication to the HoA andthe CoA of the MN 710, e.g. so as to increase the total downlinkcapacity to the MN 710. Naturally, this may require that the MN 710 isarranged so as to combine the data packets or similar from the tworouts. Such combining may e.g. be facilitated if the HA 712 or similarprovides marks or similar to the data packets or similar in thecommunication so as to indicate the order in which they are supposed tobe combined by the MN 710. The combining as such would then be easy fora person skilled in the art.

Structure of a Mobile IP-System According to a Second Embodiment of theInvention

The attention is now directed to a second exemplifying proxy Mobile IPsystem 800 according to an embodiment of the invention as illustrated inFIG. 11. The system 800 is the same as previously discussed withreference to FIGS. 7, 8, 9 and 10. However, the WiFi-based home network714 in has been replaced by an exemplifying telecommunication network814 in the form of a General Packet Radio Service system (GPRS system)comprising various network elements and interfaces as shown in FIG. 11.

The structure and operation of a general GPRS system are well known tothose skilled in the art and it needs no detailed explanation.Information about GPRS systems and similar systems as the UMTS can e.g.be found in the specifications released by the 3^(rd) GenerationPartnership Project (3GPP), se e.g. www.3gpp.org. Nevertheless, a briefoverview of an exemplifying GPRS network is given below. Before weproceed it should be emphasized that the home network 814 is by no waylimited to a GRPS network or similar. On the contrary, the invention canbe implemented in connection with most telecommunication systems oftoday, e.g. such as GSM, EDGE, CDMA, WCDMA and the HSDPA and similar.

The main Core Network (CN) elements in the GPRS network 800 are theServing GPRS Support Node (SGSN) 510, the Gateway GPRS Support Node(GGSN) 520, and upgraded location registers such as the Visitor LocationRegister (VLR) 530 and the Home Location Register (HLR) 540. The SGSN510 and the GGSN 520 may be connected directly and/or throughintermediate routers and switches to form parts of the CN. In addition,it should be emphasized that a SGSN 510 and a GSGSN 520 may be fully orpartly arranged in the same physical unit and/or as spatially separatedequipments, e.g. equipments arranged at different geographicallocations. The CN is used as the interface between a Radio AccessNetwork (RAN)—as will be elaborated below—and various external datanetworks such as e.g. a Public Data Network (PDN). Here, as shown inFIG. 11, the PDN is the communication network 130. As previouslydescribed, the communication network 130 may e.g. be the Internet orsimilar.

The GGSN 520 operates as an interface between the CN and the variousPDNs through the GPRS Gi-interface. At the other end the SGSN 510operates as an interface between various RANs.

If the RAN is a GSM EDGE Radio Access Network (GERAN) the SGSN 510interfaces through the GPRS Gb-interface. Typically, the GERAN comprisesone or several Base station Sub-Systems (BSS) 560, which in turncomprises one or several Base Station Controllers (BSC) 570 at one endbeing connected to the SGSN 510 via said Gb-interface, and at the otherend connected to a plurality of Base Transmission Stations (BTS) 580 viaa GPRS Abis-interface. A BTS 580 is in turn serving one or severalMobile Stations (MS) 590 via a GPRS Um-interface, which is an airinterface.

In addition, if the RAN is a Universal Terrestrial Radio Access Network(UTRAN) the SGSN 510 interfaces through the GPRS IuPS-interface.Typically, the UTRAN comprises one or several Radio Network Systems(RNS) 660, which in turn comprises one or several Radio NetworkControllers (RNC) 670 at one end being connected to the SGSN 510 viasaid IuPS-interface, and at the other end connected to a plurality ofNodeBs 680 via a GPRS Iub-interface. Each NodeB is in turn serving oneor several Mobile Equipments (ME) via a GPRS Uu-interface, which is anair interface.

The SGSN 510 maintains signaling connections with the HLR 540 and aMobile Switching Centre (MSC) and the VLR 530 through the GPRSGs-interface and the GPRS Gr-interface respectively. The GGSN 520maintains signaling connections with the HLR 540 through the GPRSGc-interface. A BSC 570 maintains signaling with the MSCNLR 530 throughthe GPRS A-interface, whereas a RNC maintains signaling with the MSCNLR530 through the GPRS IuCS-interface. The interconnection between theSGSN 510 and GGSN 520 are implemented through the GPRS Gn-interface.

The CN in GPRS can e.g. use the Internet Protocol (IP) as the protocolin the network layer. The protocols used in the transport layer can e.g.be the Internet User Datagram Protocol (UDP) for IP services and theInternet Transmission Control Protocol (TCP) for services which requiredelivery guarantee such as X.25 services.

The above description of the exemplifying GPRS network 814 correspondsin general to the 3GPP standard and particularly to the specificationsin the 3GPP 28-series and 48-series regarding Signal Protocols RSS-CN.

As can be seen in FIG. 11, the exemplifying proxy Mobile IP system 800is preferably provided with the same or at least similar AR/MPA 722 aspreviously described with reference to FIGS. 7, 9 and 10. However,regarding the previously discussed HA 712 it is preferred that thefunctions of the HA 712 are preformed by the GGSN 520 in the GPRSnetwork 814 or a node arrangement in the network 814 comprising the GGSN520 or being connected to the GGSN 520. For example, some functions ofthe previously discussed HA 712 may be performed by the GGSN 520 whereasother functions may be performed by other nodes in the network 814,which nodes are arranged to operatively communicate with the GGSN 520.In addition, the GGSN 520 may itself be distributed over several nodesin the network 814.

The MN 710′ in the Mobile IP system 800 is preferably provided with theMobile IP capability to signal its location to a Home Agent in the sameor similar manner as previously described with reference to the MN 710in FIGS. 7 and 8 etc. It is also preferred that the MN710′ in the MobileIP system 800 is provided with the ability to access the GPRS network814 and the communication network 130 in the same or similar manner asan ME 690. The MN 710′ may e.g. be provided with additional radiocircuit, antenna and control unit for communicating with the GPRSnetwork 814 in the same or similar manner as previously described withreference to the MN 710 in FIG. 8, whereby the control unit supports thecommunication with all the networks 714, 724 and 814. This is well knownper se to those skilled in the art and it needs no further description.

The present invention has now been described with reference toexemplifying embodiments. However, the invention is not limited to theembodiments described herein. On the contrary, the full extent of theinvention is only determined by the scope of the appended claims.

1. A network node arrangement (722) arranged to be operatively connectedto a foreign network (724) for communicating with at least one MobileNode (710, 710′), characterized in that said node arrangement (722) is:arranged to operatively provide at least one advertisement message tosaid Mobile Node (710, 710′), which advertisement message identifiessaid node arrangement (722) as a Home Agent for said Mobile Node (710,710′), arranged to operatively receive a request for an IP-address fromsaid Mobile Node (710, 710′) as a response to said advertisementmessage, arranged to operatively provide an IP-address to said mobilenode (710, 710′) as a response to the request, which IP-address is validfor the Mobile Node (710, 710′) at the foreign network (724), andarranged to operatively register a Care-of-Address on behalf of saidMobile Node (710, 710′) at another Home Agent (712, 520) in a homenetwork (714, 814) of said Mobile Node (710, 710′).
 2. The nodearrangement (722) according to claim 1, characterized in that said nodearrangement (722) is: arranged to operatively provide said advertisementmessage to said Mobile Node (710) via a wired interface or an airinterface of the foreign network (724).
 3. The network node arrangement(722) according to claim 1, characterized in that said node arrangement(722) is: arranged to operatively receive communication from the HomeAgent (712, 520), and arranged to operatively forward said communicationto the Mobile Node (710, 710′) via the foreign network (724).
 4. Thenetwork node arrangement (722) according to claim 1, characterized inthat said node arrangement (722) comprises: an Access Router (AR)arranged to operatively provide said advertisement, and receive saidrequest for an IP-address, and provide said IP-address, and a MobilityProxy Agent (MPA) arranged to operatively register said Care-of-Addresson behalf of said Mobile Node (710, 710′).
 5. The network nodearrangement (722) according to claim 1, characterized in that said nodearrangement is: arranged to be operatively connected to a communicationnetwork (130), and arranged to operatively register said Care-of-Addressvia said communication network (130).
 6. A method for registering aCare-of-Address on behalf of a Mobile Node (710) at a Home Agent (712)in a home network (714) of said Mobile Node (710) when the Mobile Nodeis connected to a foreign network (724), which method comprises thesteps of: providing at least one advertisement message to said MobileNode (710) from a network node arrangement (722) in the foreign network(724), which advertisement message identifies the node arrangement (722)as a Home Agent for said Mobile Node (710), receiving a request for anIP-address from said Mobile Node (710) at said node arrangement (722) asa response to said advertisement message, providing an IP-address tosaid Mobile Node (710) from said node arrangement (722) as a response tothe request, which IP-address is valid for the Mobile Node (710) at theforeign network (724), and registering a Care-of-Address from said nodearrangement (722) on behalf of said Mobile Node (710) at the Home Agent(712) in the home network (714) of said Mobile Node (710).
 7. Thenmethod according to claim 6 characterized in that said method comprisesthe steps of: providing said advertisement message to said Mobile Node(710) via a wired interface or an air interface of the foreign network(724).
 8. Then method according to claim 6 characterized in that saidmethod comprises the steps of: receiving communication from the HomeAgent (712, 520) at said node arrangement (722) in the foreign network(724), and forwarding said communication from said node arrangement(722) to the Mobile Node (710, 710′).
 9. Then method according to claim6 characterized in that said method comprises the steps of: using anAccess Router (AR) for providing said advertisement, and receiving saidrequest for an IP-address, and providing said IP-address, and using aMobility Proxy Agent (MPA) for registering said Care-of-Address onbehalf of said Mobile Node (710, 710′).
 10. Then method according toclaim 6 characterized in that said method comprises the steps of:connecting the node arrangement (722) to a communication network (130),registering said Care-of-Address via said communication network (130).11. A Mobile Node (710, 710′) arranged to be operatively connected to anetwork node arrangement (722) in a foreign network (724), characterizedin that said Mobile Node (710, 710′) is: arranged to operatively receiveat least one advertisement message from said node arrangement (722),which advertisement message identifies said node arrangement (722) as aHome Agent for said Mobile Node (710, 710′), arranged to operativelytransmit a request for an IP-address to said node arrangement (722) as aresponse to said advertisement message, arranged to operatively receivean IP-address from said node arrangement (722) as a response to therequest, which IP-address is valid for the Mobile Node (710, 710′) atthe foreign network (724), and arranged to operatively have aCare-of-Address registered by said node arrangement (722) on behalf ofsaid Mobile Node (710, 710′) at another Home Agent (712, 520) in a homenetwork (714, 814) of said Mobile Node (710, 710′).
 12. The Mobile Node(710, 710′) according to claim 11, characterized in that said MobileNode (710, 710′) is: arranged to operatively receive said advertisementmessage from said node arrangement (722) via a wired interface or an airinterface of the foreign network (724).
 13. The Mobile Node (710, 710′)according to claim 11, characterized in that said Mobile Node (710,710′) is: arranged to operatively receive communication from the HomeAgent (712, 520) via said node arrangement (722) which is arranged tooperatively forward said communication to the Mobile Node (710, 710′)via the foreign network (724).
 14. The Mobile Node (710, 710′) accordingto claim 11, characterized in that said Mobile Node (710, 710′)comprises: at least a first interface arrangement (810, 812) foroperatively communicating with said Home Agent via said home network(714), and at least a second interface arrangement (724) for operativelycommunicating with said Home Agent via said foreign network (724). 15.The Mobile Node (710, 710′) according to claim 14, characterized in thatsaid Mobile Node (710, 710′) is: arranged to operatively receivecommunication simultaneously from said Home Agent (712, 520) via saidhome network (714, 814) of said Mobile Node (710, 710′) and via saidnode arrangement (722) in said foreign network (724).
 16. The MobileNode (710, 710′) according to claim 1, characterized in that said MobileNode (710, 710′) is: arranged to operatively receive communication fromsaid Home Agent (712, 520) via said home network (714, 814) on a firstHome Address (HoA) and via said node arrangement (722) in said foreignnetwork (724) via a Foreign Address (HoA′).